The present invention relates generally to i methods for the extraction of lipids and cholesterol from food protein. More specifically, the invention relates to methods for the removal of fat and cholesterol from undenatured protein materials such that the product protein is suitable for human consumption, does not have its flavor adversely affected and is neither denatured nor has its functionality altered or destroyed.
Dairy whey, and generally all animal proteins, are associated with lipids which typically include cholesterol. The lipid content of whey protein concentrate is generally about 8% although various grades of whey protein have lipid contents as low as 4% or even 2%. Dried dairy whey protein also comprises from about 100 to 200 mg cholesterol/100 g whey protein concentrate. Egg yolk is particularly high in fat and cholesterol and comprises about 40-45% lipid and about 2500 mg cholesterol/100 g of material.
Various methods are known for the extraction of lipids and cholesterol from dairy and other protein materials. Christie, William W., Lipid Analysis, pp. 30-41, 176-197 (1973) discloses the use of various solvents and solvent mixtures for the extraction of lipids from animal, plant or bacterial tissues. A preferred solvent is disclosed to be a 2:1 (v/v) mixture of chloroform and methanol. This solvent system is said to be capable of readily extracting most simple and complex lipids although the addition of acid or inorganic salts is said to be required for the extraction of polyphosphoinositides of brain tissue. Other solvents are disclosed to include ethanol which is said to be effective for the extraction of lipids from liver homogenates; ethanol and diethyl ether which are useful for the removal of lipids from lipoprotein fractions; methanol and water; and chloroform, methanol and water. Solvents containing ethyl ether and chloroform are generally effective at extracting lipids and cholesterol but tend to leave undesirable residues which make the product material unsuitable for human consumption. The problem of toxic residues may, in part, be avoided by use of solvents such as hexane or alcohols. Such solvents tend, however, to be less effective in the extraction of fat and cholesterol than the more toxic solvents.
Hubbard, et al., J. Amer. Oil Chemists Soc., 54, 81-83, (1977) disclose methods for the extraction of cholesterol, fat and fatty acids from food products. The methods involve digestion of sample materials with HCl and extraction with solvents such as ethyl ether, a 2:1 solution of chloroform and methanol and solutions of chloroform, methanol and water. Such solvents are generally effective at extracting lipids and cholesterol but tend to leave undesirable residues which make the product material unsuitable for human consumption.
Kasahara, et al., U.S. Pat. No. 4,295,853 issued Oct. 20, 1981, disclose methods for assaying of lipoperoxides wherein the lipoperoxides are extracted by means of solvents such as alcohols, ketones, hydrocarbons and solvents such as dimethylsulfoxide and dimethyl formamide. An extraction solvent comprising ethanol and carbon tetrachloride is identified as being particularly preferred. Unfortunately, the use of carbon tetrachloride also tends to leave undesirable residues, rendering the product material unsuitable for human consumption.
Melnick, U.S. Pat. No. 3,563,765 issued Feb. 16, 1971, discloses methods for the extraction of fat and cholesterol from egg yolk using non-polar solvents such as hexane, cyclohexane, heptane, trichloroethylene and the like. The reference states that when extracting egg yolk solids with non-polar solvents, there appears to be little, if any, damage to the functional properties of the remaining protein. More efficient extraction is said to be possible where a polar solvent such as an alcohol is used to disrupt lipid-protein bonds, thus permitting the subsequent extraction of lipids by a non-polar solvent such as ethyl ether. Alternatively, the two processes may be combined through use of solvent mixtures such as ethanol-ether.
Such extraction methods are of limited utility when it is intended to utilize the reduced lipid/cholesterol containing protein material as a base for food products. The use of materials such as chloroform as solvents in food processing is generally unsuitable where their presence in food products is limited by health concerns. The use of some solvents, including chloroform, also causes denaturation of food proteins, thus rendering the product materials unsuitable for certain uses. Hexane is widely utilized for the removal of lipids from egg and soy protein material but solubilizes relatively little cholesterol present in whey protein concentrate. Absolute ethanol is generally acceptable for use as a solvent in food protein products, but is a relatively poor solvent for cholesterol.
Of interest to the present invention is the disclosure of U.S. Pat. No. 4,734,287, which discloses methods for the production of proteinaceous water-dispersible macrocolloid whey particles which in a hydrated state have a substantially smooth, oil-in-water emulsion-like, organoleptic character. The methods for production of the macrocolloid material involve heating undenatured and substantially soluble whey protein concentrate in the presence of selected ingredients under high shear conditions to form substantially spheroidal particles. It is critical that prior to processing to produce the macrocolloid material that the protein premix remain undenatured and substantially soluble. It is thus important that preprocessing steps not cause denaturation or adversely affect the solubility of the protein. Moreover, any preprocessing steps should be consistent with the use of the product as an ingredient in foodstuffs and should not create undesirable flavors, odors or color and should not leave residues of toxic or other undesirable chemical components in the product.